Why I continue to tolerate my wife's gambling habit?

My wife has been gambling on and off for 10 years. There are periods when she was able to be clean for 2 to 3 years. But things like a miscarriage brought her back to gambling. After she was able to conceived through IVF I thought maybe her problem might finally ended. But no, she went on a gambling spree when she was 6 month pregnant and then stopped again. I tried to convince myself that it's the hormonal imbalance that driven her to relapse. Now my daughter is 15 month old she suddenly has signs of gambling again.